Watch 101: What is a Power Reserve?

Feb 8, 2018

Article By: Logan Hannen

What is up, watchfam?! Today, we’re going to take a look at one of the most important features of any mechanical watch – the power reserve.

So a bit of a refresher – mechanical watches are powered by kinetic energy stored in the movement’s main spring which, as it becomes released and unwound, powers the gears and, by extension, the rest of the watch. It is the amount of time that the piece takes to release this energy to the rest of the movement that would be classified as the piece’s power reserve. Really, the name is pretty straightforward once you know what it means, but still worth explaining.

Mechanical Watch Movement Source: Gentleman’s Gazette

Why does this matter, though? As long as the thing works, right? Well, not exactly. See, the biggest gripe so many people have about their mechanical watch is that, if they have it in rotation with another watch or a whole collection, then every time they go to wear the thing, they need to reset the time and either wind it manually or give it the old Seiko shuffle to get the thing started up again. It’s the textbook definition of a first world problem, but hey, isn’t that what we’re here for?

The standard power reserve of a mechanical watch these days is around 40 hours or so, give or take. This is about as close to two full days as you’re likely to get, and indeed some do go a bit longer than that. Some, by contrast, go significantly longer. Take the Swatch Sistem51, which holds a pretty astonishing 90 hour power reserve, or the IWC Big Pilot series, which boasts 8 days of power reserve, stopping itself after 7 to maintain the final day as an emergency supply, if need be.

Some of these pieces indicate the amount of power left in the movement through the use of an indicator on the dial, while others simply rely on you taking notice of the slower time keeping. Whichever direction they choose to go, though, one thing is for sure: your mechanical watch nowadays is far better equipped to go the distance than it ever has been before, and will always help you to keep it classy, watchfam.